(a) Field of the Invention
This invention generally relates to a sand type hourglass with a reset mechanism. More particularly, but not by way of limitation, to an hourglass with a return duct that may be used to reset the hourglass by providing a bypass duct around the narrowed portion of the hourglass.
(b) Discussion of Known Art
In spite of great advancements in the development of time keeping mechanisms, the well known hourglass has endured as a robust device with numerous applications. Examples of these applications include the timing of plays, such as in chess, or the timing of cooking processes, such as the proper amount of time required to boil an egg in order to achieve a desired amount of firmness in the cooked egg. However, a serious drawback to the hourglass has been the absence of a mechanism that allows the hourglass to be reset or re-started without having to wait for the sand to complete its transfer from one side of the hourglass to the other.
Examples of known devices include U.S. Pat. No. 441,661 to Hawley, which teaches a clock that is based on a sand clock or hour glass. The hour glass incorporated into the Hawley device includes a valve that provides adjustment for the flow from one of the sand reservoirs. This arrangement, however, does not provide or suggest a solution for the need to reset the clock.
U.S. Pat. No. 3,125,849 to Wachtel teaches yet another hourglass type device. The Wachtel device includes a pair of reservoirs or chambers which are used to hold the sand that is delivered through a narrow duct between the reservoirs. The duct includes ans in-line valve or flow adjustment mechanism that can be used to vary the rate at which the sand flows through the duct. Thus, in order to speed up the flow of the sand from one reservoir to the next, the Wachtel device provides for an adjustment in the flow through the duct.
A more recent invention is taught in U.S. Pat. No. 5,023,852 to Mikels. The Mikels patent recognizes the long felt need to provide a mechanism that allows expedited transfer of the sand from one of the reservoirs on the next. To address this need, the Mikels device includes a valve along the neck or constriction of the hour glass. This valve is movable from a position where the flow of sand is constricted through the neck or duct between the two reservoirs to a position where the neck provides little restriction to the flow. Thus, to reset the hourglass with the Mikels device one simply opens the valve along the neck to allow unimpeded flow through the neck.
A review of known devices taught in foreign patent documents reveals that the intuitive approach at solving the problem of having to wait for an hourglass to complete its cycle is by placing a valve within the constriction between the two reservoirs. For example, German patent no. 623,530 shows a device with a pair of reservoirs connected by a flapper type valve which allows relatively unrestricted flow in one direction while providing the restricted, controlled flow in the opposite direction.
A similar approach at varying the amount of time required to transfer the sand from one reservoir to the next is shown in British patent no. 23,894 to Watkins. The Watkins device includes a pair of reservoirs connected by a neck or constricted duct that allows the controlled flow of sand from one reservoir to the next. The Watkins device is an approach that is very similar to other known devices in that it also uses a valve type mechanism that cooperates with the neck portion to vary the flow through the neck portion of the device.
Known devices that provide a means for determining different amounts of time with an hourglass include British patent no. 10,156, and British patent no. 15,564. Therefore, a review of known devices reveals that there remains a need for an hourglass that can be reset quickly and easily.
Still further, there remains a need for an hour glass that allows the user to measure different periods of time.
Still further, there remains a need for an hourglass that may be easily reset and which does not use a valve along the neck or constriction between the two reservoirs. The inclusion of a valve along the neck can lead to adverse effects in the precision of the device. Still further, the inclusion of a valve along the neck make the entire device vulnerable to fouling due to jamming of the valve by sand that works its way into the moving parts of the valve.